Chapter XI 

 THE HISTORY OF ANIMAL LIFE AND ITS INTERPRETATION 



Fundamental Considerations. As the student of Biology be- 

 comes aware of the tremendous variety of living forms now existing 

 in the world about him, so with the dawn of civilization there 

 arose an awareness of the variety of life. Man has always, by fact or 

 legend, attempted to account for his own existence and to trace his 

 own history. Similarly, interest in the origins of all living forms is 

 very old. In searching for materials with which to begin a study of 

 the history of animals, it is obvious that living organisms, other 

 than Man, do not leave written records; consequently, the history 

 must be inferred from the forms as they exist now, from such 

 skeletons and fossils as may be found, and from some certainties or 

 regularities that may be observed to have occurred in all material 

 things. Constant change is the constant fact which characterizes all 

 things that the human mind may be aware of, changes that are not 

 chaotic and haphazard but orderly and interrelated. This was recog- 

 nized early in recorded human history and the idea that things at 

 present are derived in an orderly fashion from things of the past 

 dates back to the time of Greek civilization and no doubt still earlier. 

 The doctrine of evolution is an interpretation of the history of 

 matter which holds that these changes over periods of time are from 

 the simple toward the complex, that earlier more primitive and 

 more simple conditions have as the result of orderly change given 

 rise to present complex conditions. Evolution as a broad concept 

 comprehends Celestial Evolution, or the origins of the celestial 



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